U.S. Pat. No. 7,473,846 to Doerr discloses a reversible cable support arm. As shown in FIG. 7, a cable support arm 24 is connected to rails 108. The cable support arm has a mounting bracket 92 connected to an end thereof and the lower portion 100 of the mounting bracket 92 has multiple keyhole slots 94 and a plunger 98. The inner slide member 112 of the rails comprises one or multiple boss members 116 and an aperture. The mounting bracket 92 on one end of the cable support arm 24 is fixed to the inner slide member 112 by inserting the boss members 116 into the keyhole slots 94 and by the plunger 98 inserted into the aperture of the inner slide member 112.
On the other hand, an attachment mechanism 52 is connected to the other end of the cable support arm 24 and connected to the outer slide member 110 of the rails 108. The outer slide member 110 comprises a plunger 132. The attachment mechanism 52 comprises a securing portion 120 which has an aperture 134 with which the plunger 132 of the outer slide member 110 is engaged, such that the cable support arm 24 is connected to the outer slide member 110.
The rails are installed to a rack housing 22 of the rack mount system 10 and a device 12, 14, 16, 18 or 20 can be installed to the rails. However, the connection between the rails and the cable support arm 24 is mainly relied to the insertion of the plungers 98 and 132 into the holes of the corresponding object, and the plungers 98 and 132 protrude out from the device and which occupy the room in the housing. The connection between the rails and the cable support arm has to be improved so as to maintain the room or even to enlarge the room.